Structural characterization and spectroscopic properties of imidazolium chlorobismuthate(III): [C3H5N2]6[Bi4Cl18]

The crystal structure of [C3H5N2]6Bi4Cl18 has been determined at 293 K by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group, C2/m. The structure is composed of the discrete Bi4Cl186- anions and three kinds of the imidazolium cations. The cations appeared to be disordered. The infrared spectra of [C3H5N2]6Bi4Cl18 were measured in the region of the internal vibration of the imidazolium cations (4000–400 cm−1) between 11 and 300 K. The temperature changes of wavenumbers of the δ(ring), δ(C–H) and ω(C–H) modes in the vicinity of the 195 and 221 K clearly indicate the contribution of the imidazolium cations motion to the phase transition mechanism taking place in the [C3H5N2]6Bi4Cl18 crystal.